class BookProcessingError(Exception):
    """电子书处理异常基类"""
    pass

class InvalidEpubFileError(BookProcessingError):
    """无效的EPUB文件异常"""
    pass

class VocabularyProcessingError(BookProcessingError):
    """词汇处理异常"""
    pass

class NLTKResourceError(BookProcessingError):
    """词汇处理异常"""
    pass

class DataProcessError(BookProcessingError):
    """词汇处理异常"""
    pass
